Piezoelectric driving module for lens

Abstract

A piezoelectric driving module for lens, which defines a photographic optical axis and includes a housing, a driven object (e.g., a lens module), a piezo member, and a rubbing element. The piezo member and the rubbing element are provided in the housing and located on two lateral sides of the driven object respectively. The piezo member drives the driven object by friction so that the driven object can be moved along the photographic optical axis until focused. Meanwhile, a predetermined frictional force is generated between the rubbing element and the driven object to reduce a gravity-induced speed difference between forward and backward movements of the driven object along the photographic optical axis.

What is claimed is: 
     
       1. A piezoelectric driving module for lens, defining a photographic optical axis and comprising:
 a housing having a receiving space therein; 
 a driven object received in the receiving space; 
 at least a piezo member provided on the housing and adjacent to a first lateral surface of the driven object; 
 a rubbing element provided on the housing and adjacent to a second lateral surface of the driven object, wherein the second lateral surface may or may not coincide with the first lateral surface, and the photographic optical axis is parallel to the first lateral surface and the second lateral surface; wherein when a voltage is applied to the at least a piezo member, the at least a piezo member drives the driven object to move along the photographic optical axis such that a predetermined frictional force is generated between the rubbing element and the driven object to reduce a speed difference of the driven object that results from a force of gravity acting on the driven object while the driven object is moved; 
 a pre-pressing element provided on the housing so as to apply a pre-pressing force to the at least a piezo member and thereby keep the at least a piezo member in contact with the driven object; and 
 a cover for positioning the driven object in the receiving space and limiting a position of the pre-pressing element with respect to the housing; 
 wherein the pre-pressing element is a metal plate provided behind the at least a piezo member, and the pre-pressing element has two end portions each provided with a resilient member, the two resilient members being respectively and resiliently fitted in two recesses on an outer lateral surface of the housing so as for the pre-pressing element to apply a predetermined pressing force to a back of the at least a piezo member to ensure constant contact between the at least a piezo member and the driven object. 
 
     
     
       2. The piezoelectric driving module of  claim 1 , wherein a ratio of speeds at which the driven object is moved in one direction and an opposite direction of the photographic optical axis respectively is controlled to be within 1:1.3. 
     
     
       3. The piezoelectric driving module of  claim 1 , wherein each said piezo member is a piezoelectric motor, and the driven object is a lens module selected from the group consisting of a zoom lens module and a focusing lens module. 
     
     
       4. The piezoelectric driving module of  claim 1 , further comprising at least a position detection module, wherein the at least a position detection module is provided on the housing and configured for detecting an extent to which the driven object is moved along the photographic optical axis. 
     
     
       5. The piezoelectric driving module of  claim 1 , further comprising a guiding mechanism connected to the driven object, located in the receiving space, and configured for guiding the driven object along the photographic optical axis, wherein the guiding mechanism comprises one of a guide post and a guide rail. 
     
     
       6. The piezoelectric driving module of  claim 1 , further comprising a friction element provided on the driven object so that at least a piezo member and the rubbing element can rub against the friction element. 
     
     
       7. The piezoelectric driving module of  claim 6 , wherein the friction element is cylindrical, is secured in a connecting groove of the driven object by adhesive bonding, is movable along a slide rail formed as a semicircular groove on an inner periphery of the housing so as to move linearly along the photographic optical axis in synchronization with the driven object, and is in contact with the at least a piezo member and the rubbing element. 
     
     
       8. The piezoelectric driving module of  claim 6 , wherein the friction element is made of metal or ceramic, is bonded to an inner periphery of the housing, is located on a lateral side of the at least a piezo member, and is in contact with the rubbing element so as to generate the predetermined frictional force.